Is there any documentation regarding the architecture of the nextcloud android app (like class diagrams, etc.)?
At this very moment, no. The app “has simply been written” before the fork and we added a lot of new features over time. We are however working on moving the app towards the MVP pattern, where https://github.com/nextcloud/android/pull/2504 will the first of possibly numerous changes which will push for a proper architecture.
Okay. Thanks for the quick answer!